Media handing devices that process media rely on optical (track) sensors situated throughout the devices for purposes of tracking the media and/or verifying the authenticity of the media. This is particularly relevant for currency notes. Many foreign governments have started printing currency with windowed sections. This is being done to thwart counterfeiters.
Furthermore, governments keep introducing these windowed portions as different sections of the media from what has previously been noted in the industry, which makes accounting for all the different variations and permutations extremely difficult. That is, when a government introduces a middle section of a currency note as being transparent and proper configuration of media handling devices are achieved, the same government or a different government may introduce a currency note where the first section of a currency note is transparent and additional configuration is needed. Another complication is that the consumer can insert currency notes in any orientation meaning upside down, backend first, and the like; such that configurations of the media handling devices have to be configured to handle the various orientations that the consumer may insert a windowed note into the devices.
This presents some challenges for existing optical sensors within existing media devices because the optical sensors fail to detect the presence of the windowed portion of the currency note. When an opaque document is in the path of an optical track sensor, the track sensor reports a blocked condition indicating the presence of media (such as a currency note or a check). When the document passes over and by the optical sensor, the track sensors report an unblocked condition indicating that the track no longer has media above and/or below the track sensors.
With windowed media, when the windowed (transparent) portion of the media is in the path of an optical sensor, the track sensor falsely reports the unblocked condition indicating the absence of any media. These false readings due to portions of a media document being windowed make it difficult for determining whether a windowed portion of a media document has passed over the sensor or whether the entire media document has passed over the sensor, which makes the task of locating and tracking windowed media extremely difficult.